1. Technical Field
The present invention relates to storage adapters. More specifically, it relates to the virtualization of an SAS (Serial Attached Small Computer System Interface) adapter for logical partitions of a computer system.
2. Background Information
Large computer systems are usually partitioned into a number of logical partitions. Each logical partition represents a division of resources in the system and operates as an independent logical system. An example of logical partitions is the partitioning of a multiprocessor computer system into multiple independent servers, each with it own processors, main storage, and I/O devices.
A typical resource that each logical partition requires is disk storage. Many systems utilize SAS devices to provide storage. SAS is a data transfer technology designed to replace parallel SCSI (Small Computer System Interface) with added performance, scalability and redundancy. It can provide SATA (Serial Advanced Technology Attachment) compatibility and interoperability, cost-effective tiered storage deployments, and flexibility in disk drive and platform choices.
A drawback to current implementations of the logical partitions is that each partition is required to have its own storage adapter. Hence, for a large computer system, a large number of physical storage adapters are needed, and, to provide the associated PCI (Peripheral Component Interconnect) or PCI Express adapter slots for these adapters, a large number of enclosures are also required, which lead to significant additional expenses. Current implementations also require that each partition has its own storage devices, which results in an excess number of storage devices and the corresponding enclosures used to house them. Moreover, each enclosure typically is packaged as a single SAS domain so that the enclosure is limited to a single partition. Therefore, a partition that needs a single device (or a couple of devices) must bear the cost of the complete enclosure that may have many empty device slots, which also causes a significant waste of resources.